Interest in the percutaneous or transdermal delivery of peptides and proteins to the human body continues to grow with the increasing number of medically useful peptides and proteins becoming available in large quantities and pure form. The transdermal delivery of peptides and proteins still faces significant problems. In many instances, the rate of delivery or flux of polypeptides through the skin is insufficient to produce a desired therapeutic effect due to their large size and molecular weight. In addition, polypeptides and proteins are easily degraded during and after penetration into the skin, prior reaching target cells. Likewise, the passive transdermal flux of many low molecular weight compounds is too limited to be therapeutically effective.
One method of increasing the transdermal delivery of agents relies on pretreating the skin with, or co-delivering with the beneficial agent, a skin permeation enhancer. A permeation enhancer substance, when applied to a body surface through which the agent is delivered, enhances the transdermal flux of the agent such as by increasing the permselectivity and/or permeability of the body surface, and/or reducing the degradation of the agent.
Another method of increasing the agent flux involves the application of an electric current across the body surface referred to as “electrotransport.” “Electrotransport” refers generally to the passage of a beneficial agent, e.g., a drug or drug precursor, through a body surface, such as skin, mucous membranes, nails, and the like. The transport of the agent is induced or enhanced by the application of an electrical potential, which results in the application of electric current, which delivers or enhances delivery of the agent. Electrotransport delivery generally increases agent delivery and reduces polypeptide degradation during transdermal delivery.
There also have been many attempts to mechanically penetrate or disrupt the skin in order to enhance the transdermal flux, such as, U.S. Pat. No. 5,879,326 issued to Godshall, et al., U.S. Pat. No. 3,814,097 issued to Ganderton, et al., U.S. Pat. No. 5,279,544 issued to Gross, et al., U.S. Pat. No. 5,250,023 issued to Lee, et al., U.S. Pat. No. 3,964,482 issued to Gerstel, et al., Reissue 25,637 issued to Kravitz, et al., and PCT Publication Nos. WO 96/37155, WO 96/37256, WO 96/17648, WO 97/03718, WO 98/11937, WO 98/00193, WO 97/48440, WO 97/48441, WO 97/48442, WO 98/00193, WO 99/64580, WO 98/28037, WO 98/29298, and WO 98/29365. These devices use piercing elements or microprotrusions of various shapes and sizes to pierce the outermost layer (i.e., the stratum corneum) of the skin. The microprotrusions disclosed in these references generally extend perpendicularly from a thin, flat member, such as a pad or sheet. The microprotrusions in some of these devices are extremely small, some having dimensions (i.e., a microblade length and width) of only about 25-400 μm and a microblade thickness of only about 5-50 μm. Other penetrating elements are hollow needles having diameters of about 10 μm or less and lengths of about 50-100 μm. These tiny stratum corneum piercing/cutting elements are meant to make correspondingly small microslits/microcuts in the stratum corneum for enhanced transdermal agent delivery or transdermal body analyte sampling therethrough. The perforated skin provides improved flux for sustained agent delivery or sampling through the skin. In many instances, the microslits/microcuts in the stratum corneum have a length of less than 150 μm and a width which is substantially smaller than their length.
When microprotrusion arrays are used to improve delivery or sampling of agents through the skin, consistent, complete, and repeatable microprotrusion penetration is desired. Manual application of a skin patch including microprotrusions often results in significant variation in puncture depth across the microprotrusion array. In addition, manual application results in large variations in puncture depth between applications due to the manner in which the user applies the array. Accordingly, it would be desirable to be able to apply a microprotrusion array to the stratum corneum with an automatic device which provides microprotrusion skin piercing penetration in a consistent and repeatable manner.
Another problem with microprotrusion arrays concerns their handling by the user or a medical technician. Those microprotrusion arrays having the form of a thin, flat pad or sheet having a plurality of microprotrusions extending roughly perpendicular therefrom are especially difficult to handle manually without piercing the skin of the handler's fingers. Even if an automatic applicator is used to apply the microprotrusion array to the patient, the microprotrusion array must still be mounted on the applicator. However, during mounting or loading of the microprotrusion array onto an automatic applicator device sterility of the microprotrusions may be compromised or injury to the user may occur.
Accordingly, it would be desirable to provide a retainer for holding a microprotrusion member for connection to a reusable impact applicator device for applying the microprotrusion member to the stratum corneum.